First Australian Pliocene Molossid Bat: Mormopterus (Micronomus) Sp
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Records of the Western Allstralzall Mllsellm Supplement No. 57: 291-298 (1999). First Australian Pliocene molossid bat: Mormopterus (Micronomus) sp. from the Chinchilla Local Fauna, southeastern Queensland l 2 Suzanne J. Hand!, Brian S. Mackness , Cecil E. Wilkinson and Doris M. Wilkinson2 1 School of Biological Science, University of New South Wales, NSW 2052; email: [email protected] 29 Birkett Street, Chinchilla, Qld 4413 Abstract - An isolated upper canine from the Pliocene Chinchilla Local Fauna of southeastern Queensland is identified as representing the Australian molossid genus Mormopterus, subgenus Microllomlls. It is the first Australian Pliocene representative of the cosmopolitan family Molossidae and the first Tertiary representative of the Microl1omlls lineage. Approximately six Microl1omlls species are today widely distributed across the Australian mainland, Papua New Guinea and Ambon, and are found in most habitat types from desert to rainforest. The discovery of an indeterminate species of Microl1omlls in the Chinchilla Local Fauna does not contradict the palaeoenvironmental interpretation of the area as woodland savannah. INTRODUCTION Superfamily Vespertilionoidea Gray, 1821 A variety of taxa has been recovered from the early (Weber, 1928) to middle Pliocene freshwater fluviatile Chinchilla Family Molossidae Gray, 1821 Sand northwest of Chinchilla, southeastern Queensland (Archer 1977, 1982; Archer and Dawson Monnopterns (Micronomus) sp. 1982; Bartholomai 1962, 1963, 1966, 1967, 1971, 1973, 1975, 1976; Bartholomai and Woods 1976; Dawson Material Examined 1982; Flannery and Archer 1983; Gaffney 1981; QM F30575, a left upper canine (Figure 1). Gaffney and Bartholomai 1979; Godthelp 1990; Measurements: Length 1.17 mm, width 0.98 mm, Hutchinson and Mackness submitted; Kemp and height 1.93 mm. Molnar 1981; Mackness and Scanlon in press; Olson 1975, 1977; Patterson and Rich 1987; Woods 1956, Locality and Age 1960, 1962; Wroe and Mackness 1998). Collectively North bank of the Condamine River, this assemblage is known as the Chinchilla Local Chinchilla Rifle Range (26°48'S., 1500 41'E.). The Fauna (Archer and Bartholomai 1978; Woodbume et Chinchilla Sand was named by Woods (1960) for al. 1985; Rich et al. 1991). a sequence of weakly consolidated grey to This paper describes an isolated canine recovered yellowish and light brown sands, ferruginized from the Chinchilla Sand which represents the first heterogeneous conglomerates, grits, sandy clay Australian Pliocene representative of the and clays. These outcrops range from shallow cosmopolitan family Molossidae, and the first beds to sections several metres deep. Tertiary representative of the modern Australian Wilkinson's Quarry has been continuously molossid lineage Micrononws. Two older molossids, worked by two of us (C.E.W., D.M.W.) for over described from Miocene deposits at Riversleigh in ten years. The specimen described comes from a northwestern Queensland, are members of extinct fossil-bearing unit within the quarry that lies molossid lineages (Hand 1990; Hand et aL 1997). unconformably on top of an indurated layer of Taxonomy and dental terminology follow fine sand. The sediments are primarily fluviatile Legendre Hand (1990) and Strahan (1995). in nature and represent a number of depositional The prefix QM 12 indicates specimens registered in events. Most fossils in these units occur as the fossil collection of the Queensland Museum, isolated pieces. Brisbane. Tedford et aL (1992) concluded that the Chinchilla Local Fauna biocorrelates with the Kanunka Local Fauna of the Tirari Desert, South Australia. On the SYSTEMATIC PALAEONTOLOGY basis of magnetostratigraphy, they concluded that the latter is approximately 3.4 million years old, or Suborder Microchiroptera Dobson, 1875 late early Pliocene in age. 292 S.J. Hand, B.S. Mackness, C.E. Wilkinson, D.M. Wilkinson B Figure 1 Mormopterus (Micronomus) sp., from the Pliocene Chinchilla Local Fauna, southeastern Queensland. QM F30575, left upper canine. A, posterior view; B, lingual view; C-C', stereopair, antero-occlusal view. Scale bar = 1 mm. Description such that the anterolingual blade is convex and the QM F30575 is massively-rooted with a tall, posterolingual crest concave. There is no slender, dominant main cusp (Figure 1). There is a development of a secondary cusp on either blade. narrow cingulum around the whole tooth and a The crown is flattened on the lingual side, and the small but distinct posterolingual cingular cusp. lingual margin is very straight (i.e., in occlusal view There are no other cingular cusps. The basal outline it is neither concave nor convex). The anterobuccal of the crown is subtriangular. The antero- and face is marked by a broad groove which is posterolingual corners of the main cusp (paracone) attenuated towards the apex of the cusp. This are defined by vertical crests; the posterobuccal groove results in a distinct concavity in the surface is convex. The shaft is recurved posteriorly anterobuccal margin of the crown and contributes Pliocene rnolossid from Chinchilla 293 to the tooth's triangular (rather than semi-circular) anterior cingular cusp. It differs from nycteridids in occlusal outline. In occlusal view, there is also a its flattened (rather than concave) lingual face and broad and marked indentation in the posterobuccal lack of anterior cingular cusp, and from margin, perhaps for the following tooth (but see rhinolophids in its complete and conspicuous Remarks below). The massive root is oval in cross cingulum. section with a deep groove longitudinally bisecting The Chinchilla canine differs from those of most its flattened lingual face. noctilionoids (phyllostomids, mormoopids and noctilionids) in having a distinctive anterior groove. Remarks However, some phyllostomines (e.g., P!zyllostomus and Trac!zops species) do possess a broad groove on Comparisons Made the anterior face of the shaft as well as a less Its small size, complete cingulum, flattened developed one on the anterobuccal face. But these lingual face and lack of posterior heel suggest that are large species with much larger canines, which QM F30575 is the upper canine of a usually also differ in having a rather bilobed lingual microchiropteran bat. Megachiropteran canines are margin. Many stenodermatines differ in having a generally larger, lack a complete cingulum (absent dorsal expansion of the buccal face of the canine. In buccally, variably developed lingually and Vampyrum the shaft is flattened in front but, like the posteriorly) and are generally not subtriangular in Chinchilla tooth, it has a moderately developed cross-section. Many megachiropteran canines (e.g., cingulum and distinct posterolingual cingular cusp. Pteropus spp.) have very conspicuous ridges on the In most phyllostomines (e.g., Micronycteris), the shaft; in others a secondary cusp is formed by slight upper canine is simple with the anterior shaft elongation of the cingulum (e.g., Nyctimene spp.) or smoothly rounded and with a well-developed is developed on the posterior edge of the shaft (e.g., cingulum but no extra cusps. In desmodontine species of Pteralopex and Harpyionycteris; the latter phyllostomids, the canine is large, long and narrow, may have well-developed posterior and lingual with an acute point and very sharp cutting edge. cingula and/or posterolingual basal cusps). Like the In the other phyllostomid subfamilies (America's Chinchilla canine, species of Macroglossus, glossophagines, stenodermatines, phyllonycterines) Syconycteris, Notopteris and Eonycteris have a deep there is even more variation in the basic form of the longitudinal groove on the anterior face of the shaft upper canine, making generalizations difficult. (in Melonycteris the groove is bounded by sharp Miller (1907) has described the dentition of many ridges), but otherwise differ strikingly from the taxa in this speciose group, and the following fossil in their very weak and incomplete cingula comparisons with the Chinchilla canine can be and rounded or square basal outline. made. In glossophagines, the canine tends to be The Chinchilla canine has been compared with simple with a slightly developed cingulum and no representatives of all microchiropteran groups, secondary cusps, though in some species (e.g., except the monotypic Craseonycteridae and Leptonycteris) the cingulum is obsolete but Tomopeatinae. It differs strikingly from represented anteriorly and posteriorly by short, emballonurid and rhinopomatid canines in its well-developed cusps. In other species (e.g., subtriangular occlusal outline, anterior groove and Sturnira) the inner surface is strongly concave and lack of well-developed anterior and posterior cusps thus unlike the Chinchilla tooth. Stenodermatine and/or cingular cusps. In most emballonuroids canines appear to be quite unlike the Chinchilla (e.g., R!zinopoma, Emballonura and New World tooth. In many stenodermatines, the canine is nearly diclidurines), there is no distinct cingulum, lateral as long as tall, the cingulum is well developed and compression is marked, heel development common, there are no secondary cusps; in some species (e.g., and anterior and posterior cusps are developed at Ardops, P!zyllops and Ariteus) the canine is only just the base of the anterior and posterior cutting edges. taller than the large premolar. In other The upper canines of species of Taphozous and stenodermatines (e.g., Brac!zyp!zylla) the lingual Saccolaimus have very large heels and deep, well cingulum forms two low but very distinct cusps